In various types of machinery, it is a continuing problem to seal the opening through which a rotatable shaft protrudes. The problem is manifested in the difficulty of preventing leakage or loss of pressure or loss of vacuum while at the same time avoiding undue shaft friction. As will be appreciated, shaft friction can generate heat, cause loss of power, and even damage the machinery.
One method of effecting a seal at a joint between a stationary element and a rotatable shaft has been through the use of packing, stuffing, or the like. However, packing or stuffing causes considerable friction on the shaft. Another method of effecting a seal has been to utilize O-rings. However, O-rings are subject to wear particularly when utilized with shafts that operate at high speed.
Another problem with conventional seals is that, for the most part, the machinery has to be stripped or dismantled for replacement purposes. The necessity for stripping or dismantling the machinery is most undesirable particularly where the machinery being sealed is large and heavy. Moreover, in order to replace conventional mechanical seals, the machinery must oftentimes be shut down for prolonged periods of time resulting in enormous losses in productivity.
As a result, it has been recognized as desirable to provide the parts of a mechanical seal which are subject to wear in split fashion so that they can be easily mounted and later disassembled for repair or replacement purposes. This was successfully accomplished in my earlier U.S. Pat. Nos. 4,215,870 and 4,423,878 issued, respectively, on Aug. 5, 1980 and Jan. 3, 1984, and seals manufactured according to my patents have been installed and proven to be highly effective not only in terms of their sealing capabilities but also in terms of their drastic reduction in down time of expensive machinery used in costly processes. With the features of the inventions of my earlier patents, a split-type seal has been provided which can be easily assembled and disassembled relative to machinery without interfering with the positioning or mounting of the stationary element and the rotatable shaft associated with it.
With attempts prior to my earlier patents to provide a split-type seal, it had been a problem to maintain a complete seal at all times completely about the rotatable shaft. During operation, the seals could easily become worn or deteriorated and the wear and deterioration could be non-uniform circumferentially about the shaft because of a number of reasons such as misalignment of the shaft with respect to the machinery with which it is used, or due to other factors. However, I was able to provide a sealing assembly which overcame the problem of non-uniform wearing or deterioration of the seal parts.
As set forth in my earlier U.S. Pat. No. 4,423,878, I later became aware of still additional problems requiring a solution. For instance, sealing assemblies are oftentimes needed in emergency situations. This is particularly true in applications which advantageously utilize the rotatable shaft seal disclosed and claimed in my earlier U.S. Pat. No. 4,215,870 where a seal is quickly needed on machinery used, for instance, in dangerous manufacturing processes such as the grinding of caustic chemicals and the like where time is of the essence and the seal must be made available in the field on extremely short notice. However, the shafts of such machinery vary significantly in size. Since time is of the essence in these applications, and it is not feasible to custom order a split seal from the manufacturer, field service personnel have been required to stock a large variety of seals in order to be able to service a customer on a timely basis.
In my earlier U.S. Pat. No. 4,423,878, I successfully overcame these problems with a unique sealing assembly, kit and method for rotatable shafts. This was done by providing a separate insert adapted to be mounted in an insert-receiving opening in the stationary seal member wherein a shaft-receiving opening in the insert is initially dimensioned so as to be smaller than a rotatable shaft and is thereafter adapted to be enlarged in the field before use so as to generally conform to the rotatable shaft. With this arrangement, the sealing assembly is uniquely suited to be selectively supplied in kit form.
Despite the significant advances offered by my earlier U.S. Pat. Nos. 4,215,870 and 4,423,878, I have become aware of still other problems with shaft seals. In particular, it is simply impossible to provide rotatable collars with exactly the dimension of any given shaft due to the normal range of tolerances for shafts. Accordingly, without precise machining by the ultimate user, leakage can occur which is entirely unacceptable in numerous applications where dangerous materials are involved.
The present invention is directed to overcoming the above stated problems and accomplishing the stated objects.